IBM's MQSeries® is a set of middleware products that allow user applications to intercommunicate using messages, without having to know the complexities of the underlying hardware and software platform. Applications communicate using the MQSeries application programming interface (API), issuing such calls as MQPUT to put a message onto a queue and MQGET to get a message from a queue. In this specification, the terms “get” and “put” are used generally interchangeably with the terms “read” and “write”, respectively. MQSeries is described in such publications as MQSeries Planning Guide, IBM GC33-1349-07 (January 1999), incorporated herein by reference.
The IBM S/390® Parallel Sysplex® configuration is a cluster of interconnected processing nodes with attachments to shared storage devices, network controllers, and core cluster technology components, consisting of coupling facilities, coupling support facilities, and external time references (ETRs). A coupling facility (CF) enables high-performance read/write sharing of data by applications running on each node of the cluster through global locking and cache coherency management mechanisms. It also provides cluster-wide queuing mechanisms for workload distribution and message passing between nodes.
The coupling facility is described in the following patents and publications, incorporated herein by reference:    “IN A MULTIPROCESSING SYSTEM HAVING A COUPLING FACILITY, COMMUNICATING MESSAGES BETWEEN THE PROCESSORS AND THE COUPLING FACILITY IN EITHER A SYNCHRONOUS OPERATION OR AN ASYNCHRONOUS OPERATION”, by D. A. Elko et al., Ser. No. 08/420,893, filed Apr. 11, 1995, now U.S. Pat. No. 5,561,809;    “Sysplex Shared Data Coherency Method And Means”, by D. A. Elko et al., Ser. No. 07/860,805, filed Mar. 30, 1992, now U.S. Pat. No. 5,537,574;    “Method And Apparatus For Distributed Locking Of Shared Data, Employing A Central Coupling Facility”, by D. A. Elko et al., Ser. No. 07/860,808, filed Mar. 30, 1992, now U.S. Pat. No. 5,339,427;    “Command Quiesce Function”, by D. A. Elko et al., Ser. No. 07/860,330, filed Mar. 30, 1992, now U.S. Pat. No. 5,339,405;    “Software Cache Management Of A Shared Electronic Store In A Sysplex”, by D. A. Elko et al., Ser. No. 07/860,807, filed Mar. 30, 1992, now U.S. Pat. No. 5,457,793;    “Multiple Processor System Having Software For Selecting Shared Cache Entries Of An Associated Castout Class For Transfer To A DASD With One I/O Operation”, by D. A. Elko et al, Ser. No. 07/860,806, filed Mar. 30, 1992, now U.S. Pat. No. 5,493,668;    “Command Execution System For Using First And Second Commands To Reserve And Store Second Command Related Status Information In Memory Portion Respectively”, by D. A. Elko et al., Ser. No. 07/860,378, filed Mar. 30, 1992, now U.S. Pat. No. 5,392,397;    “Integrity Of Data Objects Used To Maintain State Information For Shared Data At A Local Complex”, by D. A. Elko et al., Ser. No. 07/860,800, filed Mar. 30, 1992, now U.S. Pat. No. 5,331,673;    “Management Of Data Objects Used To Maintain State Information For Shared Data At A Local Complex”, by J. A. Frey et al., Ser. No. 07/860,797, filed Mar. 30, 1992, now U.S. Pat. No. 5,388,266;    “Clearing Data Objects Used To Maintain State Information For Shared Data At A Local Complex When At Least One Message Path To The Local Complex Cannot Be Recovered”, by J. A. Frey et al., Ser. No. 07/860,647, filed Mar. 30, 1992, now U.S. Pat. No. 5,394,542;    “Coupling Facility For Receiving Commands From Plurality Of Hosts For Activating Selected Connection Paths To I/O Devices And Maintaining Status Thereof”, by D. A. Elko et al., Ser. No. 08/324,447, filed Oct. 18, 1994, now U.S. Pat. No. 5,463,736;    “Data Processing System And Method For Providing Notification In A Central Processor Of State Changes For Shared Data Structure On External Storage”, by J. A. Frey et al., Ser. No. 07/860,809, filed Mar. 30, 1992, now U.S. Pat. No. 5,390,328;    “Method And Apparatus For Performing Conditional Operations On Externally Shared Data”, by J. A. Frey et al., Ser. No. 08/383,532, filed Feb. 1, 1995, now U.S. Pat. No. 5,742,830;    “Apparatus And Method For List Management In A Coupled Data Processing System”, by J. A. Frey et al., Ser. No. 07/860,633, filed Mar. 30, 1992, now U.S. Pat. No. 5,410,695;    “Interdicting I/O And Messaging Operations In A Multi-System Complex”, by D. A. Elko et al., Ser. No. 07/860,489, filed Mar. 30, 1992, now U.S. Pat. No. 5,394,554;    “Method And Apparatus For Coupling Data Processing Systems”, by D. A. Elko et al., Ser. No. 07/860,803, filed Mar. 30, 1992, now U.S. Pat. No. 5,317,739;    “Authorization Method For Conditional Command Execution”, by D. A. Elko et al., Ser. No. 08/408,446, filed Mar. 22, 1995, now U.S. Pat. No. 5,450,590;    “Dynamically Assigning a Dump Space in a Shared Data Facility to Receive Dumping Information to be Captured”, by D. A. Elko et al., Ser. No. 08/471,895, filed Jun. 7, 1995, now U.S. Pat. No. 5,664,155;    “Method And System For Capturing and Controlling Access To Information In A Coupling Facility”, by D. E. Neuhard et al., Ser. No. 08/146,647, filed Nov. 1, 1993, now U.S. Pat. No. 5,630,050;    “Method and System for Determining and Overriding Information Unavailability Time at a Coupling Facility”, by D. A. Neuhard et al., Serial. No. 08/779,196, filed Jan. 6, 1997, now U.S. Pat. No. 5,875,484;    “Requesting a Dump of Information Stored within a Coupling Facility, in Which the Dump Includes Serviceability Information from an Operating System That Lost Communication with the Coupling Facility”, by D. A. Neuhard et al., Ser. No. 08/779,195, filed Jan. 6, 1997, now U.S. Pat. No. 5,860,115;    “Method and Apparatus for Expansion, Contraction, and Reapportionment of Structured External Storage Structures”, by D. J. Dahlen et al., Ser. No. 08/304,458, filed Sep. 12, 1994, now U.S. Pat. No. 5,581,737;    “Method of Managing Resources in One or More Coupling Facilities Coupled to One or More Operating Systems in One or More Central Programming Complexes Using a Policy”, by R. A. Allen et al., Ser. No. 08/607,053, filed Feb. 26, 1996, now U.S. Pat. No. 5,634,072;    “Method and System for Managing Data and Users of Data in a Data Processing System”, by R. A. Allen, Ser. No. 08/146,727, filed Nov. 1, 1993, now U.S. Pat. No. 5,465,359;    “Method and System for Reconfiguring a Storage Structure Within a Structure Processing Facility”, by R. A. Allen et al., Ser. No. 08/544,941, filed Oct. 18, 1995, now U.S. Pat. No. 5,515,499;    “Method for Coordinating Executing Programs in a Data Processing System”, by R. A. Allen et al., Ser. No. 08/439,269, filed May 9, 1995, now U.S. Pat. No. 5,604,863;    “Coherence Controls for Store-Multiple Shared Data Coordinated by Cache Directory Entries in a Shared Electronic Storage”, by K. S. Carpenter et al., Ser. No. 08/148,707, filed Nov. 8, 1993, now U.S. Pat. No. 5,544,345;    “Method and System for Log Management in a Coupled Data Processing System”, by R. V. Geiner et al., Ser. No. 08/632/683, filed Apr. 15, 1996, now U.S. Pat. No. 5,737,600; and    J. M. Nick et al., “S/390 cluster technology: Parallel Sysplex”, IBM Systems Journal, vol. 36, no. 2, 1997, pages 172-201.
In the field of this invention it is known that fuzzy backup of a database can be achieved by copying the database in parallel with updates by a database engine to create a ‘fuzzy’ backup, and then (if required) restoring the database from that fuzzy backup and forward recovering it by application of log records cut by the database engine which describe the updates that were performed since the start of the fuzzy backup.
From U.S. Pat. No. 5,884,328 there is known a database mirroring mechanism based on a fuzzy backup and incremental changes. However, this known mechanism is particularly related to maintaining replicas in real time rather than re-creating a replica later in time from earlier-recorded data.
In MQSeries systems it is possible to exploit the Coupling Facility List Structure architecture for the storage of messages on shared queues.
Since the data representing messages stored by MQSeries in a Coupling Facility List structure is able to move from one list to another as the unit of work state progresses, extending the technique of fuzzy backup to MQSeries messages stored on a Coupling Facility List structure could potentially lead to excessive amounts of logging describing deletes of data from one list and inserts of the same data to a different list. This approach would therefore have the disadvantage that lots of log records would get cut as the messages transition from key to key and from list to list.
Note, this is true not just for such an MQSeries system but for any system based upon similar principles for moving data around/accessing data.